It seems that the thoroughly evil Monsanto Corporation's technology is a double edged sword. The company's ubiquitous herbicide Roundup is the preferred substance that the US Govt. pushes South American countries to use in coca eradication programs. The thing is that Monsanto has also produced "Roundup Ready" genetically modified crops like soybeans that they have been selling in these same South American countries. These Roundup Ready crops are designed to tolerate large amounts of the herbicide being sprayed on them without dying. The weeds growing nearby are all killed and the Roundup Ready crops grow merrily along with no ill effects.
The initial crop dusting of coca fields using Roundup herbicide was a huge success. Now, it is becoming clear that the local farmers growing coca have been actively selecting and breeding any plants that survived in a dusted field to produce a Roundup Ready coca plant. Some also believe that some farmers have cross bred Roundup Ready plants with coca plants to produce plants that will not die when sprayed with Roundup.
At the end of the day, these coca farmers are finding they have to do much less weeding because the US sponsored crop dusting of their fields with Roundup kills all the weeds that used to compete with their coca plants! Gracias Amigos!
http://blog.buzzflash.com/analysis/894